Variable angle locking construct for orthopedic applications

ABSTRACT

An embodiment includes a bone fixation system comprising: a bone anchor with a tapered head, the head being threaded; and a plate that includes a void, the void including one of a counterbore or a countersink; wherein: (a) no portion of the void is threaded; (b) the void includes an inner wall; (c) the inner wall includes reliefs along its perimeter. Other embodiments are described herein.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.16/943,079, filed on Jul. 30, 2020, which will issue as U.S. Pat. No.11,564,721 on Jan. 31, 2023, which claims the benefit of U.S. patentapplication Ser. No. 16/585,762, filed on Sep. 27, 2019, now U.S. Pat.No. 10,743,922, the entire contents of each are hereby incorporated byreference in their entirety herein.

TECHNICAL FIELD

Embodiments of the invention are in the field of orthopedicapplications.

BACKGROUND

It is common practice in orthopedics to drive bone screws into bone viaholes in a fixation plate. This allows for the stabilization ofosteotomies, fractures, bone fragments, and the like. Often a user maydesire for a screw to lock to the plate to prevent the screw frombacking out from the plate after insertion of the screw into bone. Thedesired angle at which a locked screw engages a hole in the plate mayvary from normal to the central axis of the hole depending on patientanatomy or additional hardware.

BRIEF DESCRIPTION OF THE DRAWINGS

Features and advantages of embodiments of the present invention willbecome apparent from the appended claims, the following detaileddescription of one or more example embodiments, and the correspondingfigures. Where considered appropriate, reference labels have beenrepeated among the figures to indicate corresponding or analogouselements.

FIG. 1 includes a bone anchor in an embodiment.

FIGS. 2A, 2B, 2C include a top view, a perspective view, and across-sectional view of a bone plate in an embodiment.

FIGS. 3A, 3B, 3C include a side view, a cross-sectional view, and a topview of a bone plate in an embodiment.

FIGS. 4A, 4B, 4C include a side view, a cross-sectional view, and a topview of a bone plate in an embodiment.

FIGS. 5A, 5B, 5C include cross-sectional views of differing embodimentsof a bone plate.

DETAILED DESCRIPTION

Reference will now be made to the drawings wherein like structures maybe provided with like suffix reference designations. In order to showthe structures of various embodiments more clearly, the drawingsincluded herein are diagrammatic representations of structures. Thus,the actual appearance of the fabricated structures, for example in aphoto, may appear different while still incorporating the claimedstructures of the illustrated embodiments. Moreover, the drawings mayonly show the structures useful to understand the illustratedembodiments. Additional structures known in the art may not have beenincluded to maintain the clarity of the drawings. For example, not everyportion of a device is necessarily shown. “An embodiment”, “variousembodiments” and the like indicate embodiment(s) so described mayinclude particular features, structures, or characteristics, but notevery embodiment necessarily includes the particular features,structures, or characteristics. Some embodiments may have some, all, ornone of the features described for other embodiments. “First”, “second”,“third” and the like describe a common object and indicate differentinstances of like objects are being referred to. Such adjectives do notimply objects so described must be in a given sequence, eithertemporally, spatially, in ranking, or in any other manner. “Connected”may indicate elements are in direct physical or electrical contact witheach other and “coupled” may indicate elements co-operate or interactwith each other, but they may or may not be in direct physical orelectrical contact. Phrases such as “comprising at least one of A and B”include situations with A, B, or A and B.

An embodiment includes a variable angle locking screw and plate systemthat does not require the plate include a threaded or tapered hole.Locking the screw to the plate allows for the biomechanical load to betransferred from the screw to the plate in a more efficient manner thanwould be the case with standard non-locking screw/plate systems. Theload transfer may aid in the healing process as the reduction of, forexample, the osteotomy or fracture is maintained.

An embodiment includes a bone fixation system comprising a bone anchor101 and a plate 151. While the plate in FIG. 2A shows a single aperture,this is for clarity and embodiments may include 1, 2, 3, 4, 5, 6 or moreholes.

The bone anchor includes a head 102, a body 103, and a long axis 104.The body has an outer diameter 105 that is orthogonal to the long axisand the head has an outer diameter I06 that is orthogonal to the longaxis. While the body is not tapered in Figure I other embodiment mayhave a tapered body wherein (a) the thread root 107 (where a threadmeets the non-threaded portion of the body) may be tapered, (b) thethread crest (outermost edge of thread) may be tapered, (c) thread rootand thread crest are both tapered at the same angle of incidence to thelong axis, or (d) thread root and thread crest are tapered at differentangles of incidence to the long axis. In FIG. 1 the outer diameter ofthe head diameter 106 is greater than the outer diameter of the body105.

The plate includes an aperture 152 and the aperture includes a long axis153 that traverses the aperture but does not intersect the plate. Theaperture includes a first opening 154 and a second opening 155. Theaperture includes a projection 156 and the projection projects inwardlyfrom a wall 157 of the aperture and towards the long axis. Theprojection has a first surface 158 and a second surface 159. At least aportion of the first surface is coplanar with a first plane 160. Thefirst plane 160 intersects the long axis at a first angle 161 which is90 degrees. However, in other embodiments the first angle is between 85degrees and 95 degrees, between 75 degrees and 105 degrees, or between65 degrees and 115 degrees.

Projection 156 includes an inner wall 162 that couples the first surfaceof the projection to the second surface of the projection. The innerwall of the projection has a first portion 163 that is a first distance164 from the long axis 153, the first distance being orthogonal to thelong axis. The inner wall of the projection has a second portion 165that is a second distance 166 from the long axis, the second distancebeing orthogonal to the long axis. The second distance is greater thanthe first distance due to portion 165 being in a void, recess, or reliefformed along the wall 162. In an embodiment the inner wall of theprojection has a third portion 167 that is a third distance 168 from thelong axis, the third distance being orthogonal to the long axis. Thethird distance is greater than the first distance.

In an embodiment the third distance 168 is greater than the seconddistance 166 (not shown in FIG. 2A). Thus, reliefs may be formed atvarying depths that are unequal to each other. The second distance ismeasured from a location of the second portion that is furthest from thelong axis as compared to other locations of the second portion (i.e.,the deepest portion of the relief) and the third distance is measuredfrom a location of the third portion that is furthest from the long axisas compared to other locations of the third portion.

In an embodiment the inner wall of the projection defines an innerperimeter of the projection. The inner wall of the projection has afourth portion 169 that is the first distance 164 from the long axis.

In an embodiment distance 166 is between 0.508 mm and 1.016 mm and isgreater than distance 164 by a differential distance 184 and thedifferential distance is between 0.127 mm and 0.381 mm.

In an embodiment at least a portion of the second surface is coplanarwith a second plane 170. The second plane intersects the long axis at asecond angle 171 which is 90 degrees. However, in other embodiments thesecond angle is between 85 degrees and 95 degrees, between 75 degreesand 105 degrees, or between 65 degrees and 115 degrees.

In FIG. 2C the first surface 158 is a first distance 172 from the firstopening, the first distance being parallel to the long axis. The secondsurface is a second distance 173 from the second opening, the seconddistance being parallel to the long axis. The first distance is greaterthan the second distance. This may allow greater clearance for the plateto accept a bone anchor to thereby allow a greater angle of insertion ofthe anchor into the plate. However, in other embodiments these distancesmay be the same.

In an embodiment distance 173 is between 0.254 mm and 1.27 mm anddistance 172 is between 0.254 mm and 5.588 mm. In an embodiment portion163 of the projection projects inwardly from the wall 157 of theaperture and towards the long axis by distance 185 which is between0.254 mm and 0.127 mm. In an embodiment thickness 186 is between 1.00 mmto 2.75 mm.

Dimensions as used herein are examples and various embodiment may or maynot include such dimensions.

In an embodiment the plate 151 includes no threads between the first andsecond openings 154, 155. The first opening 154 directly interfaces afirst outer surface 174 of the plate; the second opening 155 directlyinterfaces a second outer surface 175 of the plate; and the first outersurface 174 of the plate opposes the second outer surface 175 of theplate. By avoiding the use of threads, the locking angle can beincreased without shearing the projection material off or creatingburrs. Additionally, once a screw is locked in a threaded construct atan angle, the threads are damaged and relocking at different angles maybe difficult. Avoiding threads allows for high angulation and repeatedlocks. Additionally, one is not limited by just one screw design orthread profile, unlike many other conventional locking constructs.

In an embodiment the first opening has a first maximum diameter (twiceradius 176 in the example of FIG. 2C) that is orthogonal to the longaxis and the second opening has a second maximum diameter (twice radius177 in the example of FIG. 2C) that is orthogonal to the long axis. Inan embodiment the second maximum diameter is greater than the firstmaximum diameter but in other embodiments the two diameters may be equalor the first diameter may be greater than the second diameter.

In FIG. 3B the head 102 of the bone anchor includes a maximum diameter106. Plate opening 154 maximum diameter 176′ is greater than the maximumdiameter 106. Also, projection 156 forms a ring that circumnavigates aninner portion of the aperture. The ring has a minimum diameter 164′ thatis less than the maximum diameter 106. As used herein, a “maximum”diameter may accommodate situations where, for example, a surface is notcircular. For example, opening 154 may be non-circular in someembodiments and therefore include more than one diameter such that the“maximum” diameter is the largest of the multiple diameters.

In an embodiment the maximum diameter 106 of the head of the bone anchoris between 5 percent and 10 percent larger than the minimum diameter164′ of the ring.

In Figure I at least a portion of the head 102 of the bone anchor isincluded in a proximal-most fifth (20 percent) of the bone anchor andthe portion includes threads. In other words, at least a portion of thebone anchor head is threaded. In Figure I the body 103 of the boneanchor includes threads. The threads of the body of the bone anchor havea first thread height 178 and the threads of the portion of the head ofthe bone anchor have a second thread 179 that is less than the firstthread height.

In FIG. 1 the threads of the body of the bone anchor have a first crestwidth 180 and the threads of the portion of the head of the bone anchorhave a second crest width 181 that is greater than the first crestwidth. However, in other embodiments the widths 180, 181 are equal toeach other and in still other embodiments width 181 that is less thanwidth 180.

In FIG. 1 thread height 179 is between 0.0254 mm and 0.3048 mm and crestwidth 181 is between 0.0508 mm and 0.3048 mm.

In FIGS. 1, 3C, and 4C the head of the bone anchor has a circularcross-section, the cross-section being orthogonal to the long axis ofthe bone anchor; and the outer diameter of the head is greater than theouter diameter of the body based on the bone anchor including a taperedportion. The tapered portion includes a thread root that tapersoutwardly at an angle 182 between 10 degrees and 20 degrees. The threadsof the portion of the head of the bone anchor include thread crests thattaper outwardly at an angle 183 between 10 degrees and 20 degrees.However, in other embodiments the tapered portion includes a thread rootthat tapers outwardly at an angle 182 between 10 degrees and 25 degreesand the threads of the portion of the head of the bone anchor includethread crests that taper outwardly at an angle 183 between 10 degreesand 25 degrees.

An embodiment provides a variable angle locking construct for orthopedicapplications by allowing for interference between the locking screw andthe screw hole. In an embodiment the locking screw is a dual leadlocking screw with a tapered diameter that (measured from one or morethread crests) extends 2.2 mm to 3.5 mm. However, in other embodimentsthe locking screw is a dual lead locking screw with a tapered diameterthat (measured from one or more thread crests) extends 1.6 mm to 7.0 mm.In an embodiment the threaded portion extends throughout the length ofthe screw. The minor of the screw head is tapered by 12 degrees to 17degrees and from 8 percent to 80 percent of the total screw length. Themajor of the screw head is tapered by 7 degrees to 15 degrees but notfor the entirety of the head. The proximal portion of the screw headmajor is not tapered for 5 percent to 15 percent of the screw head. Thescrew has a minor diameter at the thread breakout 187 ranging from 6percent smaller to 3 percent larger than diameter 164′. However, inanother embodiment the screw has a minor diameter at the thread breakout187 ranging from 10 percent smaller to 5 percent larger than diameter164′.

In an embodiment the diameter of the locking threads on the anchor headrange from 1 percent to 15 percent larger than diameter 164′. Thedifference in diameters provides interference with the projection 156 tocause deformation to the aperture at the relief cuts of portions 165,167 (and any other relief cuts or portions in projection 156).

In an embodiment the anchor contains a diameter 106 that allows forlimited interference with the top surface 174 under angulated locking upto 30 degrees from axis 104. However, in another embodiment the anchorcontains a diameter 106 that allows for limited interference with thetop surface 174 under angulated locking up to 50 degrees from axis 104.

In an embodiment space 188 is formed as a counterbore with a diameter176′ 15 percent to 35 percent larger than diameter 164′. The apertureformed by sidewall 162 is coaxial with the counterbore and allows formating with the locking screw. Diameter 164′ provides interference withthe tapered head 102 and locking threads of the head. A radius 189ranging from 0.0508 mm to 0.381 mm may be present at the bottom of thecounterbore to aid in the reduction of stress or manufacturability.

The projection 156 includes a thickness 186 that 40 percent to 60percent less than the lead of the screw 190 (where a lead is the axialadvance of a helix or screw during one complete tum (360°) and whereinthe lead for a screw thread is the axial travel for a singlerevolution).

The locking hole may have a plurality of relief cuts (see, e.g.,portions 165, 167) that are radially oriented about the aperture. Thepresence of the cuts (or, more generally, voids) allows for deformationof the land to occur which aids in the interference fit with the screw.

In an embodiment anchor and plate are made of the same material. Such amaterial may include, for example, Ti-6Al-4V. However, otherbiocompatible materials may be used in other embodiments and the anchorand plate do not necessarily require the same material.

Embodiments are suitable for locking bone plates and anchors (such asscrews) used for foot/ankle treatment. However, other embodiments aresuitable for orthopedics or medicine (human or animal) in generalincluding without limitation applications in foot and ankle, spinal,craniofacial, and/or veterinary arenas and the like.

Embodiments provide for a variable angled locking construct that doesnot use a tapered plate, threaded plate, or channeled plate.

The relief cuts or voids of the plate may include, 1, 2, 3, 4, 5 or morein alternative embodiments. An embodiment has an absence of the bottomside counterbore (e.g., void 188′ is missing). Diameter 164′ may range,for example, from 1.0 mm to 7.0 mm or more. Likewise, the anchors mayvary in diameter 106 from 1.0 mm to 7.0 mm or more. In an embodiment thescrew is not fully threaded and possesses a cap at the head of the screwthat does not contain threads. In an embodiment the drive feature of thescrew can be of any feature that allows for the transmission of torquefrom a mating member. In an embodiment the threads of the screw could beembodied in a left-handed thread configuration. In an embodiment thenumber of screw leads can vary from one to four. In an embodiment thescrew head could be spherical in shape as opposed to conical in shape.

An embodiment includes a locking mechanism that locks using a mixture ofthe “cut-in”, “point loading thread-in”, and “screw head expansion” andmechanism without the use of a countersink, threaded hole, or taperedhole geometry. Compared to conventional technologies using atwo-component system for locking, locking mechanisms addressed hereinprovide a higher degree of angulation without a compromise in thelocking strength. Advantages over conventional systems include theability to lock at angles exceeding 30 degrees in one direction, whichresults in a locking cone of 60 degrees. However, in other embodimentsadvantages over conventional systems include the ability to lock atangles exceeding 50 degrees in one direction, which results in a lockingcone of 100 degrees. Additionally, an embodiment allows for multiplelocking attempts at varying angles (without using additional componentssuch as a bushing or locking cap). Instead, such an embodiment onlyrequires a locking hole and screw of certain geometries to achieve thesame result.

An embodiment includes a screw with two or more continuous threads. Thescrew includes a conical head and a cylindrical body that make up theoverall length of the screw 201. Embodiments of a screw may vary inlength from 4 mm to 170 mm. In an embodiment the length is between 8 mmto 50 mm.

In an embodiment the screw has a tapered conical head that extends tothe cylindrical body of the screw. In the embodiment the screw isgenerally cylindrical between the tapered head and the tip of the screw.

In an embodiment the diameter of the screw head is a critical dimension.The diameter 106 of the screw head is imperative for interference thatallows for the locking of the screw to the plate and which prevents thescrew from translating through the hole without “biting” or locking. Thediameter 106 of the screw head can vary from 2.4384 mm to 4.572 mm. Inthe embodiment the head diameter is equal or larger than diameter 164′.In an embodiment the diameter 106 is 7 percent larger than diameter164′. However, in other embodiments the diameter 106 is 4, 5, 6, 8, 9,10 percent larger or more than diameter 164′.

In an embodiment the thread height 178 (for the threads on the body)ranges from 0.254 mm to 0.762 mm. In an embodiment the height 178 is0.381 mm. The thread height is identical between the two threads of theembodiment of FIG. 1 but in other embodiments they can be different withone thread having a larger height than the other.

In an embodiment a critical feature is that the thread height 179 at thehead of the screw is different from the thread height 178 for the bodyof the screw. The thread height 179 is between 0.0254 mm and 0.3048 mm.In an embodiment the thread height 179 is 0.1778 mm. The height of thethread 179 in the tapered head 102 allows for ideal locking into theaperture formed by projection 156. If the thread height 179 is too high,the threads may deform and shear from the head of the screw creating anundesired burr of loose body. Conversely, if the thread height 179 istoo low, the locking can be comprised by not contributing to a cut inprojection 156.

In an embodiment a critical feature is that the minor head angle 182(i.e., angle that the root of the thread follows). This feature iscritical embodiment because it aids in the formation of the thread headgeometry. In various embodiments the angle varies from 10 to 20 degreesand extends 80 to 100 percent of the tapered head 102 from the body ofthe screw 103. However, in other embodiments the angle varies from 10 to25 degrees and extends 80 to 100 percent of the tapered head 102 fromthe body of the screw 103. The angle 182 allows for the threads on thehead to bite and wedge into the projection 156.

In an embodiment a critical feature is that the major head angle 183(i.e., angle that the thread crests follows). This feature is criticalin an embodiment because it defines the geometry of the threads on thehead. In various embodiments the angle may range from 10 to 20 degrees.However, in other embodiments the angle may range from 10 to 25 degrees.In an embodiment angle 183 is between 15 to 17 degrees. In an embodimentthis angle is constant throughout the head of the screw. The angleallows for the threads on the head to bite and wedge into projection156.

In an embodiment the leading flank angle 191 helps to define the threadgeometry and is between 30 and 40 degrees (or between 20 and 50 degreesin other embodiments). In an embodiment angle 191 is 35 degrees. In anembodiment the trailing flank angle 192 helps to define the threadgeometry and is between 2 and 8 degrees (or between 2 and 30 degrees inother embodiments). In an embodiment angle 192 is 3 degrees. In anembodiment the lead 190 of the screw (i.e., the pitch divided by eachunique thread) is between 0.7366 mm and 1.524 mm. In an embodiment thelead is 0.9906 mm. In an embodiment the crest width 180 (or flats at theedge of the threads) on the body of the screw are between 0.0254 mm and0.1524 mm.

In an embodiment a critical feature is that the crest width 181 on thehead of the screw is/are between 0.0508 mm and 0.3048 mm, with a valuebeing 0.2032 mm in an embodiment. This is critical because the crestneeds to be small enough to produce enough stress and/or strain on theprojection 156 but large enough so that it does not shear and create aloose body.

In an embodiment thread diameter 105 is the maximum diameter of thethreads at the body of the screw. In an embodiment the diameters of allunique threads are equal (e.g., if there are two unique threads on thescrew the threads are equal to each other). However, in an embodimentthe diameters of all unique threads may be different. In an embodimentdiameter I05 is about 2.6924 mm.

In an embodiment the shaft diameter 193 (defined by the diameter createdby the root of thread for the body of the screw) is equal for all uniquethreads and may be about 1.8796 mm. However, in other embodimentsdiameter 193 may be different for different unique threads. In anembodiment the tip of the screw may be rounded or sharp forself-drilling applications. In an embodiment, root 107 of the thread ismade up of two or more geometries such as radii (e.g., 0.2032 mm) and a0.0254 mm flat.

Regarding the plate, in an embodiment a critical feature includes a useof an upper counterbore. As used herein, a counterbore is a cylindricalflat-bottomed hole that enlarges another coaxial hole. The use of thecounterbore creates a flat land 158 that the locking screw can engage.The counterbore may have a depth 172 of 0.762 mm but may range in otherembodiments from 0.254 mm to 1.27 mm. In alternative embodiments (e.g.,FIG. 5B), the upper portion of the counterbore may have a countersinkwith total included angle greater than 90 degrees from the central axis153. As used herein, a countersink includes a conical hole cut into amanufactured object. In embodiment, the counterbore radius 189 may ormay not be present and allows for manufacturability of the land feature.Such a radius may be, for example, 0.254 mm.

In an embodiment aperture reliefs are a critical component. For example,in FIG. 2A there are three reliefs but in alternative embodiments theremay be 1, 2, 4, 5 or more reliefs. The reliefs are oriented radiallyfrom the central axis 153 and are comprised of a diameter 166 rangingfrom 0.508 mm to 1.016 mm that protrudes into projection 156. Thereliefs allow for deformation of the locking hole to occur withoutcreating a loose body.

In an embodiment projection 156 (e.g., a land) is a projection ofmaterial that is radially oriented with an upper and lower surface thatmay be parallel to each other. In an embodiment there is no taper,angulation, or threaded relief to the land (e.g., there is a 90 degreeangle between wall 162 and surface 158). The land may increase along theshort axis of the locking hole (aperture formed by projection 156) ifthe underside of the locking plate is curved. The land is comprised of athickness 186 and length 185.

In an embodiment the thickness 186 is critical to the function of thelocking mechanism and is between 0.254 mm and 5.588 mm which allows forthe thread of the locking head to cut into the projection withoutcritically deforming the projection and allowing the screw to pullthrough the projection. The land thickness 186 is consistent around thecircumference of the aperture in an embodiment. In an embodimentthickness 186 varies. Such an embodiment may include, for example, stepsto vary the thickness.

In an embodiment 176′ is larger than diameter 164′ by 1.0668 mm. Thesmaller the counterbore diameter is the less angulation the screw can belocked in because the screw will contact the top surface 174. Inalternative embodiments the presence of a countersink at the top of thecounterbore circumvents this consideration.

In an embodiment a critical feature is the depth 184 of the reliefs,which may or may not be equal for each of the reliefs. Typically, thereliefs will have a depth 184 into the projection 156 from 0.127 mm to0.381 mm. In an embodiment depth 184 is 0.3048 mm. If the depth of therelief is too shallow, the locking will be compromised. Similarly, ifthe depth is too deep the land may subject to a critical force and theland will deform too much and shear from the locking plate.

In an embodiment diameter 164′ is a critical feature. The diameter isless than the head diameter 106 by 7 percent but may range from 2 to 15percent less. The diameter is critical to the design and allows for theoptimal amount of interference that allows the screw to bite/wedge intothe locking hole (hole defined by projection 156) to create a solidone-piece construct. In an embodiment, the aperture has a diameter of4.0767 mm.

In an embodiment the upper counterbore depth has a sidewall 157 parallelwith axis 153. However, a counterbore can be combined with otherfeatures such as a countersink (e.g., FIG. 5B). FIGS. 5A and 5Cillustrate other alternative designs. In an embodiment the uppercounterbore depth 172 is 0.889 mm.

In an embodiment a lower counterbore is present, but such a feature isoptional. An embodiment includes a land with two parallel planes 160,170. If a lower counterbore absent, the underside 175 may have a radiusof curvature that is not parallel to the top surface 174 of the land.The presence of a lower counterbore or void aids in providing clearanceof the locking screw at high angles. In an embodiment, the lower counterbore has a diameter 176″ of 5.461 mm and a depth 173 of 0.127 mm.

A critical feature in some embodiments is the distance 185 of theprojection of the locking hole land from the counterbore wall 157. Thisvalue may vary from 0.254 mm to 0.762 mm in various embodiments. Theprojection is critical to the locking mechanism because if theprojection is too small, the angle that the screw and the ability tolock will be compromised. Additionally, if the projection is too long,the locking screw may translate through the locking hole.

In an embodiment, the angle of the upper counterbore wall 157 from thecentral axis 153 may be 0 degrees (parallel) but may range from 0 to 80degrees in other embodiments. Further, the angle of the lowercounterbore sidewall from axis 153 may be 0 degrees but may range from 0to 80 degrees.

The following examples pertain to further embodiments.

Example 1. A bone fixation system comprising: a bone anchor; and aplate; wherein the bone anchor: (a)(i) includes a head and a body, thehead being coupled to the body, (a)(ii) has a long axis, (a)(iii) thebody has an outer diameter that is orthogonal to the long axis and thehead has an outer diameter that is orthogonal to the long axis, and(a)(iv) the outer diameter of the head is greater than the outerdiameter of the body; wherein: (b)(i) the plate includes an aperture,(b)(ii) the aperture includes a long axis that traverses the aperturebut does not intersect the plate, (b)(iii) the aperture includes a firstopening and a second opening, (b)(iv) the aperture includes a projectionand the projection projects inwardly from a wall of the aperture andtowards the long axis, (b)(v) the projection has a first surface and asecond surface, and (b)(vi) at least a portion of the first surface iscoplanar with a first plane, and (b)(vii) the first plane intersects thelong axis at a first angle and the first angle is between 85 degrees and95 degrees.

In an embodiment such a bone anchor may include what some call a“headless” screw. Such a screw may have varying pitch or lead (e.g., alarger pitch or lead near the distal end and a smaller pitch or leadnear the proximal end). However, the screw may still taper to someextent, even if the taper near the proximal end is slight.

Example 2. The bone fixation system of example 1 wherein: the projectionincludes an inner wall that couples the first surface of the projectionto the second surface of the projection; the inner wall of theprojection has a first portion that is a first distance from the longaxis, the first distance being orthogonal to the long axis; the innerwall of the projection has a second portion that is a second distancefrom the long axis, the second distance being orthogonal to the longaxis; the second distance is greater than the first distance.

Example 3. The bone fixation system of example 2 wherein: the inner wallof the projection has a third portion that is a third distance from thelong axis, the third distance being orthogonal to the long axis; thethird distance is greater than the first distance.

Example 4. The bone fixation system of example 3 wherein: the thirddistance is greater than the second distance; the second distance ismeasured from a location of the second portion that is furthest from thelong axis as compared to other locations of the second portion;

the third distance is measured from a location of the third portion thatis furthest from the long axis as compared to other locations of thethird portion.

Example 5. The bone fixation system of example 3 wherein: the inner wallof the projection defines an inner perimeter of the projection; theinner wall of the projection has a fourth portion that is the firstdistance from the long axis; the first portion is between the second andthird portions; the third portion is between the first and fourthportions.

Example 6. The bone fixation system of example 2 wherein the first planeis orthogonal to the long axis.

Example 7. The bone fixation system of example I wherein the first planeis orthogonal to the long axis.

Example 8. The bone fixation system of example I wherein at least aportion of the second surface is coplanar with a second plane, and(b)(viii) the second plane intersects the long axis at a second angleand the second angle is between 85 degrees and 95 degrees.

Example 9. The bone fixation system of example 8 wherein the secondplane is orthogonal to the long axis.

Example 10. The bone fixation system of example 8 wherein the firstplane is orthogonal to the long axis.

Example 11. The bone fixation system of example I wherein: the firstsurface is between the second surface and the first opening; the secondsurface is between the first surface and the second opening; the firstsurface is a first distance from the first opening, the first distancebeing parallel to the long axis; the second surface is a second distancefrom the second opening, the second distance being parallel to the longaxis; the first distance is greater than the second distance.

Example 12. The bone fixation system of example I wherein: the plateincludes no threads between the first and second openings; the firstopening directly interfaces a first outer surface of the plate; thesecond opening directly interfaces a second outer surface of the plate;the first outer surface of the plate opposes the second outer surface ofthe plate.

Example 13. The bone fixation system of example 12 wherein: the firstopening has a first maximum diameter that is orthogonal to the longaxis; the second opening has a second maximum diameter that isorthogonal to the long axis; the second maximum diameter is greater thanthe first maximum diameter.

Example 14. The bone fixation system of example 13 wherein: the head ofthe bone anchor includes a third maximum diameter; the first maximumdiameter is greater than the third maximum diameter; the projectionforms a ring that circumnavigates an inner portion of the aperture; thering has a minimum diameter; the minimum diameter of the ring is lessthan the third maximum diameter.

Example 15. The bone fixation system of example I wherein: at least aportion of the head of the bone anchor is included in a proximal-mostfifth of the bone anchor; the portion of the head of the bone anchorincludes threads.

Example 16. The bone fixation system of example 15 wherein: the body ofthe bone anchor includes threads; the threads of the body of the boneanchor have a first thread height; the threads of the portion of thehead of the bone anchor have a second thread height; the second threadheight is less than the first thread height.

Example 17. The bone fixation system of example 16 wherein: the threadsof the body of the bone anchor have a first crest width; the threads ofthe portion of the head of the bone anchor have a second crest width;the second crest width is greater than the first crest width.

Example 18. The bone fixation system of example I wherein the projectionforms a ring that circumnavigates an inner portion of the aperture.

Example 19. The bone fixation system of example I wherein: the head ofthe bone anchor has a circular cross-section, the cross-section beingorthogonal to the long axis of the bone anchor; the outer diameter ofthe head is greater than the outer diameter of the body based on thebone anchor including a tapered portion; the tapered portion includes athread root that tapers outwardly at an angle between 10 degrees and 25degrees; the head of the bone anchor includes a maximum diameter takenorthogonal to the long axis of the bone screw; the projection forms aring that circumnavigates an inner portion of the aperture, the ringincluding a minimum diameter; the maximum diameter of the head of thebone anchor is between 5 percent and I0 percent larger than the minimumdiameter of the ring; at least a portion of the head of the bone anchoris included in a proximal-most fifth of the bone anchor, the portion ofthe head of the bone anchor including threads; the threads of theportion of the head of the bone anchor have a thread height, the threadheight being between 0.0254 mm and 0.3048 mm; the threads of the portionof the head of the bone anchor have a crest width, the crest width beingbetween 0.0508 mm and 0.3048 mm; the first surface is between the secondsurface and the first opening and the second surface is between thefirst surface and the second opening; the first surface is a firstdistance from the first opening, the first distance being parallel tothe long axis and being between 0.254 mm and 1.27 mm; the projectionincludes an inner wall that couples the first surface of the projectionto the second surface of the projection; the inner wall of theprojection has a first portion that is a second distance from the longaxis, the second distance being orthogonal to the long axis; the innerwall of the projection has a second portion that is a third distancefrom the long axis, the third distance being orthogonal to the longaxis; the third distance is greater than the second distance and thethird distance is between 0.508 mm and 1.016 mm; the third distance isgreater than the second distance by a differential distance and thedifferential distance is between 0.127 mm and 0.381 mm; the firstsurface is a fourth distance from the second surface, the fourthdistance being parallel to the long axis and being between 0.254 mm and5.588 mm; the first portion of the projection projects inwardly from thewall of the aperture and towards the long axis by a fifth distance, thefifth distance being between 0.254 mm and 0.127 mm.

Example 19.5 The bone fixation system of example 19 wherein the threadsof the portion of the head of the bone anchor include thread crests thattaper outwardly at an angle between 10 degrees and 20 degrees.

Example 20. A bone fixation system comprising: a bone anchor with atapered head, the head being threaded; and a plate that includes a void,the void including one of a counterbore or a countersink; wherein: noportion of the void is threaded; the void includes an inner wall; theinner wall includes reliefs along its perimeter;

Example 21. The bone fixation system of example 20 wherein: the voidincludes the counterbore; the counterbore includes a landing, thelanding including a surface that is defined by a plane; the plane isorthogonal to a long axis of the void; the counterbore includes asidewall, the sidewall extending parallel to the long axis of the void.

Example 22. The bone fixation system of example 20 wherein: the boneanchor includes a material; the plate includes the material; the boneanchor is monolithic; the plate is monolithic.

Example 23. The bone fixation system of example 21 wherein: the boneanchor and the reliefs are collectively configured such that threads ofthe bone anchor head deform the landing adjacent at least one of thereliefs when the bone anchor mates with the plate; the bone anchor andthe reliefs are collectively configured to lock the bone anchor to theplate in response to the threads of the bone anchor head deforming thelanding.

Example 24. The bone fixation system of example 23 wherein the plateincludes no resilient members.

For example, some conventional techniques may use a wire (e.g.,nickel-chrome alloy with shape memory) that moves laterally while ascrew is being inserted and then snaps back medially and over the screwhead to prevent screw backout. However, no such resilient member isincluded in an embodiment of the plate.

Example 25. A bone fixation kit comprising: a plate that includes avoid, the void including one of a counterbore or a countersink; wherein:the plate includes no resilient members; no portion of the void isthreaded; the void includes an inner wall; the inner wall includesreliefs along its perimeter; the reliefs are configured such thatthreads of a bone anchor head will deform the inner wall adjacent atleast one of the reliefs when the bone anchor mates with the plate.

Example 26. The bone fixation kit of example 25 wherein: the voidincludes the counterbore; the counterbore includes a landing, thelanding including a surface that is defined by a plane; the plane isorthogonal to a long axis of the void; the counterbore includes asidewall, the sidewall extending parallel to the long axis of the void.

Example 27. The bone fixation kit of example 25 comprising the boneanchor.

Example 5a. The bone fixation system according to any of examples 3-4wherein: the inner wall of the projection defines an inner perimeter ofthe projection; the inner wall of the projection has a fourth portionthat is the first distance from the long axis; the first portion isbetween the second and third portions; the third portion is between thefirst and fourth portions.

Example 6a. The bone fixation system according to any of examples 1-5wherein the first plane is orthogonal to the long axis.

Example 8a. The bone fixation system according to any of examples 1-6wherein at least a portion of the second surface is coplanar with asecond plane, and (b)(viii) the second plane intersects the long axis ata second angle and the second angle is between 85 degrees and 95degrees.

Example 10a. The bone fixation system according to any of examples 1-9wherein the first plane is orthogonal to the long axis.

Example 11a. The bone fixation system according to any of examples 1-10wherein: the first surface is between the second surface and the firstopening; the second surface is between the first surface and the secondopening; the first surface is a first distance from the first opening,the first distance being parallel to the long axis; the second surfaceis a second distance from the second opening, the second distance beingparallel to the long axis; the first distance is greater than the seconddistance.

Example 12a. The bone fixation system according to any of examples 1-11wherein: the plate includes no threads between the first and secondopenings; the first opening directly interfaces a first outer surface ofthe plate; the second opening directly interfaces a second outer surfaceof the plate; the first outer surface of the plate opposes the secondouter surface of the plate.

Example 15a. The bone fixation system according to any of examples 1-14wherein: at least a portion of the head of the bone anchor is includedin a proximal-most fifth of the bone anchor; the portion of the head ofthe bone anchor includes threads.

Example 18a. The bone fixation system according to any of examples 1-17wherein the projection forms a ring that circumnavigates an innerportion of the aperture.

Example 19a. The bone fixation system according to any of examples 1-18wherein: the head of the bone anchor has a circular cross-section, thecross-section being orthogonal to the long axis of the bone anchor; theouter diameter of the head is greater than the outer diameter of thebody based on the bone anchor including a tapered portion; the taperedportion includes a thread root that tapers outwardly at an angle between10 degrees and 20 degrees; the head of the bone anchor includes amaximum diameter taken orthogonal to the long axis of the bone screw;the projection forms a ring that circumnavigates an inner portion of theaperture, the ring including a minimum diameter; the maximum diameter ofthe head of the bone anchor is between 5 percent and 10 percent largerthan the minimum diameter of the ring; at least a portion of the head ofthe bone anchor is included in a proximal-most fifth of the bone anchor,the portion of the head of the bone anchor including threads; thethreads of the portion of the head of the bone anchor have a threadheight, the thread height being between 0.0254 mm and 0.3048 mm; thethreads of the portion of the head of the bone anchor have a crestwidth, the crest width being between 0.0508 mm and 0.3048 mm; the firstsurface is between the second surface and the first opening and thesecond surface is between the first surface and the second opening; thefirst surface is a first distance from the first opening, the firstdistance being parallel to the long axis and being between 0.254 mm and1.27 mm; the projection includes an inner wall that couples the firstsurface of the projection to the second surface of the projection; theinner wall of the projection has a first portion that is a seconddistance from the long axis, the second distance being orthogonal to thelong axis; the inner wall of the projection has a second portion that isa third distance from the long axis, the third distance being orthogonalto the long axis; the third distance is greater than the second distanceand the third distance is between 0.508 mm and 1.016 mm; the thirddistance is greater than the second distance by a differential distanceand the differential distance is between 0.127 mm and 0.381 mm; thefirst surface is a fourth distance from the second surface, the fourthdistance being parallel to the long axis and being between 0.254 mm and5.588 mm; the first portion of the projection projects inwardly from thewall of the aperture and towards the long axis by a fifth distance, thefifth distance being between 0.254 mm and 0.127 mm.

Example 22a. The bone fixation system according to any of examples 20-21wherein: the bone anchor includes a material; the plate includes thematerial; the bone anchor is monolithic; the plate is monolithic.

As used herein, monolithic means formed of a single unit. For example,the plate may be formed by forging, machining of a block of material,additive manufacturing, and the like. Such a unit would not includewelds or portions joined via adhesives.

Example 23a. The bone fixation system according to any of examples 20-22wherein: the bone anchor and the reliefs are collectively configuredsuch that threads of the bone anchor head deform the landing adjacent atleast one of the reliefs when the bone anchor mates with the plate; thebone anchor and the reliefs are collectively configured to lock the boneanchor to the plate in response to the threads of the bone anchor headdeforming the landing.

Example 24a. The bone fixation system according to any of examples 20-23wherein the plate includes no resilient members.

Example 27a. The bone fixation kit according to any of examples 25-26comprising the bone anchor.

Example 6a′. The bone fixation system according to any of examples 5awherein the first plane is orthogonal to the long axis.

Example 8a′. The bone fixation system according to any of examples 5a-6awherein at least a portion of the second surface is coplanar with asecond plane, and (b)(viii) the second plane intersects the long axis ata second angle and the second angle is between 85 degrees and 95degrees.

Example 10a′. The bone fixation system according to any of examples 5a,6a, 8a wherein the first plane is orthogonal to the long axis.

Example 11a′. The bone fixation system according to any of examples 5a,6a, 8a, 10a wherein: the first surface is between the second surface andthe first opening; the second surface is between the first surface andthe second opening; the first surface is a first distance from the firstopening, the first distance being parallel to the long axis; the secondsurface is a second distance from the second opening, the seconddistance being parallel to the long axis; the first distance is greaterthan the second distance.

Example 12a′. The bone fixation system according to any of examples 5a,6a, 8a, 10a, 11a wherein: the plate includes no threads between thefirst and second openings; the first opening directly interfaces a firstouter surface of the plate; the second opening directly interfaces asecond outer surface of the plate; the first outer surface of the plateopposes the second outer surface of the plate.

Example 15a′. The bone fixation system according to any of examples 5a,6a, 8a, 10a, 11a, 14a wherein: at least a portion of the head of thebone anchor is included in a proximal-most fifth of the bone anchor; theportion of the head of the bone anchor includes threads.

Example 18a′. The bone fixation system according to any of examples 5a,6a, 8a, 10a, 11a, 14a, 17a wherein the projection forms a ring thatcircumnavigates an inner portion of the aperture.

Example 19a′. The bone fixation system according to any of examples 5a,6a, 8a, 10a, 11a, 14a, 17a, 18a wherein: the head of the bone anchor hasa circular cross-section, the cross-section being orthogonal to the longaxis of the bone anchor; the outer diameter of the head is greater thanthe outer diameter of the body based on the bone anchor including atapered portion; the tapered portion includes a thread root that tapersoutwardly at an angle between 10 degrees and 20 degrees; the head of thebone anchor includes a maximum diameter taken orthogonal to the longaxis of the bone screw; the projection forms a ring that circumnavigatesan inner portion of the aperture, the ring including a minimum diameter;the maximum diameter of the head of the bone anchor is between 5 percentand 10 percent larger than the minimum diameter of the ring; at least aportion of the head of the bone anchor is included in a proximal-mostfifth of the bone anchor, the portion of the head of the bone anchorincluding threads; the threads of the portion of the head of the boneanchor have a thread height, the thread height being between 0.0254 mmand 0.3048 mm; the threads of the portion of the head of the bone anchorhave a crest width, the crest width being between 0.0508 mm and 0.3048mm; the first surface is between the second surface and the firstopening and the second surface is between the first surface and thesecond opening; the first surface is a first distance from the firstopening, the first distance being parallel to the long axis and beingbetween 0.254 mm and 1.27 mm; the projection includes an inner wall thatcouples the first surface of the projection to the second surface of theprojection; the inner wall of the projection has a first portion that isa second distance from the long axis, the second distance beingorthogonal to the long axis; the inner wall of the projection has asecond portion that is a third distance from the long axis, the thirddistance being orthogonal to the long axis; the third distance isgreater than the second distance and the third distance is between 0.508mm and 1.016 mm; the third distance is greater than the second distanceby a differential distance and the differential distance is between0.127 mm and 0.381 mm; the first surface is a fourth distance from thesecond surface, the fourth distance being parallel to the long axis andbeing between 0.254 mm and 5.588 mm; the first portion of the projectionprojects inwardly from the wall of the aperture and towards the longaxis by a fifth distance, the fifth distance being between 0.254 mm and0.127 mm.

Example 23a′. The bone fixation system according to any of examples 22awherein: the bone anchor and the reliefs are collectively configuredsuch that threads of the bone anchor head deform the landing adjacent atleast one of the reliefs when the bone anchor mates with the plate; thebone anchor and the reliefs are collectively configured to lock the boneanchor to the plate in response to the threads of the bone anchor headdeforming the landing.

Example 24a′. The bone fixation system according to any of examples 22a,23a wherein the plate includes no resilient members.

The foregoing description of the embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formsdisclosed. This description and the claims following include terms, suchas left, right, top, bottom, over, under, upper, lower, first, second,etc. that are used for descriptive purposes only and are not to beconstrued as limiting. For example, terms designating relative verticalposition refer to a situation where a device side of a substrate is the“top” surface of that substrate; the substrate may actually be in anyorientation so that a “top” side of a substrate may be lower than the“bottom” side in a standard terrestrial frame of reference and stillfall within the meaning of the term “top.” The term “on” as used herein(including in the claims) does not indicate that a first structure “on”a second structure is directly on and in immediate contact with thesecond structure unless such is specifically stated; there may be athird structure or other structure between the first structure and thesecond structure on the first structure. The embodiments of a device orarticle described herein can be manufactured, used, or shipped in anumber of positions and orientations. Persons skilled in the relevantart can appreciate that many modifications and variations are possiblein light of the above teaching. Persons skilled in the art willrecognize various equivalent combinations and substitutions for variouscomponents shown in the Figures. It is therefore intended that the scopeof the invention be limited not by this detailed description, but ratherby the claims appended hereto.

1-20. (canceled)
 21. A bone fixation system, comprising: a bone anchor;and a plate; wherein the bone anchor: (a)(i) includes a head and a body,the head being coupled to the body, (a)(ii) has a long axis, (a)(iii)the body has an outer diameter that is orthogonal to the long axis andthe head has an outer diameter that is orthogonal to the long axis,(a)(iv) the outer diameter of the head is greater than the outerdiameter of the body, and (a)(v) the outer diameter of the head isgreater than the outer diameter of the body based on the bone anchorincluding a tapered portion having a thread root that tapers outwardlyat an angle between 10 degrees and 25 degrees; and wherein: (b)(i) theplate includes an aperture, (b)(ii) the aperture includes a long axisthat traverses the aperture but does not intersect the plate, (b)(iii)the aperture includes a first opening and a second opening, (b)(iv) theaperture includes a projection and the projection projects inwardly froma wall of the aperture and towards the long axis, (b)(v) the projectionhas a first surface and a second surface, (b)(vi) at least a portion ofthe first surface is coplanar with a first plane, and (b)(vii) the firstplane intersects the long axis at a first angle and the first angle isbetween 85 degrees and 95 degrees.
 22. The bone fixation system of claim21, wherein: the projection includes an inner wall that couples thefirst surface of the projection to the second surface of the projection;the inner wall of the projection has a first portion that is a firstdistance from the long axis, the first distance being orthogonal to thelong axis; the inner wall of the projection has a second portion that isa second distance from the long axis, the second distance beingorthogonal to the long axis; and the second distance is greater than thefirst distance.
 23. The bone fixation system of claim 22, wherein: theinner wall of the projection has a third portion that is a thirddistance from the long axis, the third distance being orthogonal to thelong axis; and the third distance is greater than the first distance.24. The bone fixation system of claim 23, wherein: the third distance isgreater than the second distance; the second distance is measured from alocation of the second portion that is furthest from the long axis ascompared to other locations of the second portion; and the thirddistance is measured from a location of the third portion that isfurthest from the long axis as compared to other locations of the thirdportion.
 25. The bone fixation system of claim 23, wherein: the innerwall of the projection defines an inner perimeter of the projection; theinner wall of the projection has a fourth portion that is the firstdistance from the long axis; the first portion is between the second andthird portions; and the third portion is between the first and fourthportions.
 26. The bone fixation system of claim 22, wherein the firstplane is orthogonal to the long axis.
 27. The bone fixation system ofclaim 21, wherein the first plane is orthogonal to the long axis. 28.The bone fixation system of claim 21, wherein at least a portion of thesecond surface is coplanar with a second plane, and (b)(viii) the secondplane intersects the long axis at a second angle and the second angle isbetween 85 degrees and 95 degrees.
 29. The bone fixation system of claim28, wherein the second plane is orthogonal to the long axis.
 30. Thebone fixation system of claim 28, wherein the first plane is orthogonalto the long axis.
 31. The bone fixation system of claim 21, wherein: thefirst surface is between the second surface and the first opening; thesecond surface is between the first surface and the second opening; thefirst surface is a first distance from the first opening, the firstdistance being parallel to the long axis; the second surface is a seconddistance from the second opening, the second distance being parallel tothe long axis; and the first distance is greater than the seconddistance.
 32. The bone fixation system of claim 21, wherein: the plateincludes no threads between the first and second openings; the firstopening directly interfaces a first outer surface of the plate; thesecond opening directly interfaces a second outer surface of the plate;and the first outer surface of the plate opposes the second outersurface of the plate.
 33. The bone fixation system of claim 32, wherein:the first opening has a first maximum diameter that is orthogonal to thelong axis; the second opening has a second maximum diameter that isorthogonal to the long axis; and the second maximum diameter is greaterthan the first maximum diameter.
 34. The bone fixation system of claim33, wherein: the head of the bone anchor includes a third maximumdiameter; the first maximum diameter is greater than the third maximumdiameter; the projection forms a ring that circumnavigates an innerportion of the aperture; the ring has a minimum diameter; and theminimum diameter of the ring is less than the third maximum diameter.35. The bone fixation system of claim 21, wherein: at least a portion ofthe head of the bone anchor is included in a proximal-most fifth of thebone anchor; and the portion of the head of the bone anchor includesthreads.
 36. The bone fixation system of claim 35 wherein: the body ofthe bone anchor includes threads; the threads of the body of the boneanchor have a first thread height; the threads of the portion of thehead of the bone anchor have a second thread height; and the secondthread height is less than the first thread height.
 37. The bonefixation system of claim 36, wherein: the threads of the body of thebone anchor have a first crest width; the threads of the portion of thehead of the bone anchor have a second crest width; and the second crestwidth is greater than the first crest width.
 38. The bone fixationsystem of claim 21, wherein the projection forms a ring thatcircumnavigates an inner portion of the aperture.
 39. The bone fixationsystem of claim 34, wherein: the head of the bone anchor has a circularcross-section that is orthogonal to the long axis of the bone anchor;and the third maximum diameter of the head of the bone anchor is takenorthogonal to the long axis of the bone screw.
 40. The bone fixationsystem of claim 35, wherein: the threads of the portion of the head ofthe bone anchor have a thread height, the thread height being between 0.0254 mm and
 0. 3048 mm; the threads of the portion of the head of thebone anchor have a crest width, the crest width being between
 0. 0508 mmand
 0. 3048 mm; the first surface is a first distance from the firstopening, the first distance being parallel to the long axis and beingbetween 0.254 mm and 1.27 mm; the inner wall of the projection has afirst portion that is a second orthogonal distance from the long axis,the second distance being orthogonal to the long axis; the inner wall ofthe projection has a second portion that is a third distance from thelong axis, the third distance being orthogonal to the long axis; thethird distance is greater than the second distance and the thirddistance is between
 0. 508 mm and 1.016 mm; the third distance isgreater than the second distance by a differential distance and thedifferential distance is between 0.127 mm and 0.381 mm; the firstsurface is a fourth distance from the second surface, the fourthdistance being parallel to the long axis and being between 0.254 mm and5.588 mm; and the first portion of the projection projects inwardly fromthe wall of the aperture and towards the long axis by a fifth distance,the fifth distance being between 0.254 mm and 0.127 mm.